1561620121 has 16 divisors (see below), whose sum is σ = 1692370944. Its totient is φ = 1437148944.

The previous prime is 1561620107. The next prime is 1561620131. The reversal of 1561620121 is 1210261651.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 1561620121 - 2¹³ = 1561611929 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1561620131) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 54480 + ... + 78046.

It is an arithmetic number, because the mean of its divisors is an integer number (105773184).

Almost surely, 2^1561620121 is an apocalyptic number.

It is an amenable number.

1561620121 is a deficient number, since it is larger than the sum of its proper divisors (130750823).

1561620121 is a wasteful number, since it uses less digits than its factorization.

1561620121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23700.

The product of its (nonzero) digits is 720, while the sum is 25.

The square root of 1561620121 is about 39517.3394979976. The cubic root of 1561620121 is about 1160.1793522226.

Adding to 1561620121 its reverse (1210261651), we get a palindrome (2771881772).

The spelling of 1561620121 in words is "one billion, five hundred sixty-one million, six hundred twenty thousand, one hundred twenty-one".